This invention relates to a liquid atomizer to be used for atomizing of liquids and more particularly, to a two-phase type atomizing unit which can atomize liquids such as water, liquid-fuel and the like to such an extent that the liquids atomized produce a mist of liquid with respective particle-diameters being in the range from a sub-micron order to at most some tens of microns and is easily applied to many engineering operations including atomizing operations without any difficulties at all.
Up to the present, there have been proposed and developed a number of specific types of spraying nozzles of the two phase or one phase type and, at the present, almost all forms of atomizing operations can be accomplished, provided that a suitable atomizing nozzle, i.e. one which has a specific capacity in respect to the generation of mist having a predetermined range of atomized liquid particle diameters, is only chosen properly.
In spite of this, in order to cope with a recent demand for generation of a large amount of mist of liquid having much smaller particle-diameters, i.e., respective particle-diameters are sometimes in the range from a sub-micron order to some tens of microns, hardly any suitable conventional spraying nozzles or the systems in which they are incorporated are available. Therefore, to respond to the recent trend of liquid atomization as mentioned above, the engineering in the field of liquid atomization has been further developed, thus resulting in a specific type of liquid atomizer, which is designated an ultrasonic atomizing nozzle, has been recently proposed. More specifically, the ultrasonic atomizing nozzle has an approximate double conduit shape in section and comprises an inner conduit portion for compressible fluid, and an annular conduit portion for incompressible fluid, the forward end of which is, however, closed and is communicated with the inner conduit through a plurality of holes, and a resonance chamber which is spaced from the discharging outlet of the nozzle body a predetermined distance, with an open end portion being confronted by the discharging outlet of the nozzle body. By the arrangement as described above, a flow of compressed air introduced into the conduit portion is forcibly interrupted when blocked by the inner surface of the resonance chamber, whereby a strong supersonic energy field is produced in a space which is interposed between the discharging outlet of the nozzle body and the open end portion of the chamber. The liquid inside the annular conduit portion is accordingly drawn, via holes, into a flow of compressed air through the supersonic energy field being produced, whereby the liquid is split into numerous minute liquid-particles and then is forcibly dispersed into the open air as a mist while being entrained by the air flow secondarily produced. For the generation of mist with this arrangement, the air to be introduced should be compressed at a pressure higher than 0.5 Kg/cm.sup.2 and therefore, the air compressed at a pressure ranging from 1 to 6 Kg/cm.sup.2 is conventionally introduced. Such being the case, since such highly compressed air as described above has to be supplied, employment of air compressor of the piston displacement type is indispensable. Furthermore, since the ultrasonic atomizing nozzle requires a considerable amount of compressed air, the air compressor of the above-described type must be large-size, particularly if a plurality of nozzles of the above-described type are simultaneously employed so as to constitute a mist generating system. Hence, as is well known by those skilled in the art, as far as the air compressor of the above-described type is concerned, since the amount of compressed air produced in relation to the electrical power consumed is relatively small, mist generation with the ultrasonic atomizing nozzles consequently is quite an expensive operation.
So far as the simultaneous employment of a plurality of ultrasonic atomizing nozzles is concerned, there are further undesirable problems as follows.
First of all, the use of a large-size air compressor of the piston displacement type will bring about a public nuisance due to the undesirable noise problem. In addition, when the ultrasonic atomizing nozzles are arrayed in series so as to generate a large amount of mist at the same time, the amounts of mist respectively dispersed from the ultrasonic atomizing nozzles tend to be superimposed, and frequencies of impingements of minute liquids particles are increased, thus resulting in agglomeration. The large liquid drops thus formed no longer float in the air, whereby not only is the range of dispersement of mist thus generated reduced, but also a ground field in which the atomization is carried out becomes soaking wet accordingly. The undesirable situations mentioned above can not be avoided, so long as a large amount of mist constituted by liquid-particles each having such a minute particle-diameter has to be generated with the help of more than one ultrasonic atomizing nozzle of the above-described type.